I) Cross Domain Scripting :A local user can run JavaScript code in other user's domain and accesscookies and compromise the victim website.POC : User "hacker" makes ".htmltemplates" directory in hacker's homepage(/home/hacker/.htmltemplates/) and makes "exploit" file containingJavaScript. Now this script can be called from hacker's domain(hacker.com) :http://hacker.com/cgi-sys/entropysearch.cgi?user=hacker&template=exploit

But, the script is also accessible from other hosted domains (for examplevictim.com) :http://victim.com/cgi-sys/entropysearch.cgi?user=hacker&template=exploit

Here, the hacker's code is running in another domain's area andvictim.com's cookies can be read.A demonstrative video for this vulnerability can be found here :http://opensecurity.ca/media/cpanel-cross-domain-scripting.mp4

II) Find existing system users :Any unauthorized visitor can find valid system users.POC : If the hacker calls "entropysearch.cgi" script with an invalidusername, the error message will be :"Could not chdir into /.htmltemplates: No such file or directory"http://1.2.3.4/cgi-sys/entropysearch.cgi?user=notexist

But if the hacker calls "entropysearch.cgi" script with a valid username,the error message will be :"Could not chdir into /home/victim/.htmltemplates: No such file or directory"http://1.2.3.4/cgi-sys/entropysearch.cgi?user=victim

The hacker can make a dictionary attack to find several valid usernames.

III) Find user's homepage :If a hacker knows the username, then user's homepage address can be found.POC :http://domain.com/cgi-sys/entropysearch.cgi?user=victim :"Could not chdir into /home2/victim/.htmltemplates: No such file ordirectory"

This can be useful for further attacks.

===[ Patching ]===

cPanel believes that these are not security vulnerabilities, so the issuealready exist.

===[ Timeline ]===

[06/12/2016] - Vendor notified[06/12/2016] - Vendor verified reception of the report[09/12/2016] - Vendor responded that these are not security vulnerabilities[10/12/2016] - POC video sent to vendor explaining the severity of crossdomain scripting vulnerability[06/01/2017] - No response from vendor, so vendor was contacted again[11/01/2017] - No response from vendor, public disclosure

===[ Credits ]===

Vulnerabilities have been discovered by Omid @ Open Security.

===[ References ]===

Open Security :http://opensecurity.ca/

Original Advisory :http://opensecurity.ca/2016/12/multiple-vulnerabilities-in-cpanel/